Copper lead frame: an ultimate solution to the reliability of BLPpackage

Copper lead frame was chosen as an on-board reliability enhancement for the BLP (bottom leaded plastic) package. Adopting the copper lead frame needed a verification process for the package reliability because of its high affinity with oxygen that degrades package reliability. A series of tests were performed to select the best copper material and to determine the adhesion index parameter. The experimental results showed that the adhesion strength between the copper lead frame and EMC (epoxy molding compound) was affected by alloy composition, oxide layer thickness, and cupric/cuprous oxide ratio, Among them, the adhesion index parameter proved to be the cupric/cuprous oxide ratio. When it falls between 0.2-0.3, the highest adhesion strength was obtained regardless of alloy composition and oxide thickness. From the adhesion test results, the Cr-Zr-Cu copper alloy was employed as the lead frame for the 54-pin BLP package. The package reliability and on-board reliability tests including surface mountability, mechanical robustness, and solder joint reliability were carried out to compare the 54-pin BLP package, with Cr-Zr copper alloy and alloy 42 lead frame     

Stretchable calix[4]arene-based gels by induction of water

This study focused on controlling the stretching property of gels. This resilience is dependent on the water content in the calix[4]arene-based gel solvent system, where the stretching property of gels could be controlled upon the addition of water. The storage (G′) and loss (G″) moduli of the calix[4]arene-based gels prepared in solvent systems with different water contents were investigated via rheological measurements. By the strain sweeps, the values of G′ decreased, while tan-delta increased with water content in the solvent system. In addition, a significant changes in the G′ and G″ values were observed upon the addition of water by frequency sweeps. In particular, the decrease in the G″ value of the gel prepared from the 1,3-alternated calix[4]arene derivative ( HC4 ) and diisocyanate linker ( HDI ) in DMSO/H₂O mixed solvent (8:2 v/v) was approximately 5-fold larger than that of the gel prepared in 100% DMSO. Thus, this novel approach would useful for the development of new soft materials with finely controllable mechanical properties.     

Acid tolerance and morphological characteristics of five Weissella cibaria bacteriophages isolated from kimchi

Food Science and Biotechnology - Five bacteriophages were isolated from kimchi with the hosts of two Weissella cibaria and acid-producing bacteria, and characterized for understanding Weissella...     

Development of new assay for sucrose phosphorylase and its application to the characterization of Bifidobacterium longum SJ32 sucrose phosphorylase

Sucrose phosphorylase, a hexosyltransferase, that is an important enzyme in starch and sucrose metabolisms, reversibly catalyzes the conversion of sucrose and orthophosphate to fructose and α-d-glucose-1-phosphate. A simple assay method for sucrose phosphorylase using 3,5-dinitrosalicylic acid (DNS) was developed. Its effectiveness was compared with that of a previously used NAD method. The results establish that the DNS method is comparable to the NAD method for the assay of sucrose phosphorylase. In particular, analysis of the enzyme activity level of sucrose phosphorylase (SPase) from Bifidobacterium longum SJ32 revealed that the DNS method is not only simple and accurate, but it also is a time-saving method for assaying sucrose phosphorylase activity. Most importantly, the DNS method is stable in broad pH ranges (pH 4–10), whereas the NAD method showed inaccurate profiles in the alkaline pH ranges (pH 8–10). Kinetic studies on SPase from B. longum SJ32 were performed using the simple DNS method developed in this study.     

Investigating the determinants of low adoption of tablet PCs in Korean firms: Effects of value perception and alternative attractiveness

Many IT innovations show significantly different results from the expectations or market forecasts in the diffusion perspective. Tablet PCs have gained immense attention as useful devices for improving productivity and enhancing customer relationship in firms. However, the diffusion of tablet PCs in firms has been progressing slowly. This study examines the effects of value perception and alternative attractiveness on the diffusion of tablet PCs, using survey data from Korean firms. The results reveal that perceived low benefits, monetary and non-monetary sacrifices are determinants of perceived low value, which in turn influences low adoption intention of tablet PCs. Alternative attractiveness is also significantly associated with perceived low value and low adoption intention. Furthermore, firm innovativeness moderates the relationship between perceived low value and low adoption intention. We discuss the theoretical implications on the adoption barriers of firms from the value adoption model and suggest practical implications for successful diffusion of IT innovations in firms, focused on tablet PCs.     

Molecular cloning and expression of amylosucrase from highly radiation-resistant Deinococcus radiopugnans

Amylosucrase (AS), a glucosyltransferase of the glycoside hydrolase 13 family, does not require a nucleotide-activated sugar as a glucosyl-donor. A gene (drpas) of Deinococcus radiopugnans encoding a putative AS was identified and cloned for characterization. The amino acid sequence revealed that drpas exhibited 76 and 74% identities with AS genes from D. geothermalis and D. radiodurans, respectively. Recombinant DRpAS exhibited AS activities. The ratios of hydrolysis, polymerization, and isomerization reactions were 5.8:82.7:11.5 at 40°C. The DRpAS was highly thermostable and produced more polymerization products than AS from D. radiodurans although the optimum growth temperature of both strains is 30°C.     

一株降解芘的苍白杆菌的分离、鉴定及性能表征

采用富集培养的方法从北京焦化厂多环芳烃(PAHs)污染土壤中筛选到一株高效降解芘的微生物,命名为PW,分子生物学等手段鉴定此菌株属于苍白杆菌属(Ochrobactrum sp.).经一次性大剂量方法对此菌株进行驯化后,考察了摇瓶条件下环境因素对此菌株降解芘效率的影响.结果表明,驯化培养使得菌株5d内对0.5mmol/L芘的降解率由62.3%提高到92.7%.此外,该菌株的环境耐受性好,在环境温度为20￣40℃下该菌株对芘均具有一定的降解能力,30℃培养时降解效果最好;在pH为5～10的培养基中,PW对芘的降解率均在45%以上;当盐度小于3%时,此菌株对芘降解率在60%以上;同时菌株PW还可耐受一定浓度的重金属.     

Stretchable graphene transistors with printed dielectrics and gate electrodes

With the emergence of human interface technology, the development of new applications based on stretchable electronics such as conformal biosensors and rollable displays are required. However, the difficulty in developing semiconducting materials with high stretchability required for such applications has restricted the range of applications of stretchable electronics. Here, we present stretchable, printable, and transparent transistors composed of monolithically patterned graphene films. This material offers excellent mechanical, electrical, and optical properties, capable of use as semiconducting channels as well as the source/drain electrodes. Such monolithic graphene transistors show hole and electron mobilities of 1188 ± 136 and 422 ± 52 cm(2)/(V s), respectively, with stable operation at stretching up to 5% even after 1000 or more cycles.     

Model development for diffusion with instantaneous chemical reactions in a spherical multicomponent drop

Diffusion accompanied by instantaneous chemical reactions in a multicomponent drop is modeled. The developed model is then simulated for the case of absorption of one solute from a continuous phase into the drop, followed by fast reactions with two different reactants existing in the drop. The results of the model are obtained by using Galerkin’s finite element method and represented by unsteady concentration profiles of all components in the drop, the reaction front positions, and the cumulative mass flux and the enhancement factor of the diffusing solute. The effects of the system parameters, such as diffusivities of the solute and the reactants, the relative amount of the reactants in the drop, and the interfacial concentration of the solute, on the calculated quantities are evaluated.     

The effect of block lengths on micelle structure in blends of styrene-isoprene diblock copolymer and poly(vinyl methyl ether)

The micellar structure of styrene-isoprene diblock copolymer and poly(vinyl methyl ether) blends was investigated by using small-angle X-ray scattering and transmission electron microscopy techniques. In order to determine the effect of styrene block length on the formation of micellar structure, three sets of diblock copolymers, with near-identical isoprene block molecular weights, but with different styrene block lengths were studied. With modeling based on the polydisperse Percus-Yevick hard sphere fluid model, the structural parameters characterizing the micelles were determined as a function of copolymer concentrations, temperature, and copolymer block lengths. The core radius was found to decrease on increasing the length of styrene block. The degree of swelling of the corona by PVME increased steadily with increasing the styrene block length.